Otitis media (OM) is the most common diagnosis in pediatric patients who visit physicians for illness in the United States [1-2], affects more than 90% of all children by the age of 5 [3-4], is the most common indication for antimicrobial therapy in children [5], is the most common cause of hearing loss in young children and can lead to speech, language, educational and other developmental delays [6]. Treatment of OM also consumes significant health care resources as OM is responsible for approximately $5 billion annually in health care expenditures in the U.S., is the most common cause for surgical procedures in young children [4,7-8], and is associated with life-threatening complications such as meningitis and brain abscess formation [9- 10]. Given these factors, a more thorough understanding of OM through basic science investigation is required to provide potential novel and efficacious interventions. Specifically, gel-forming mucins (GFM), produced by middle ear mucosa (MEM), are known to be the primary cause of hearing loss which develops in children with chronic OM and mucins are also known to be critically important in ME mucosal protective functions and immunity. Very little has been achieved in developing an understanding of the regulation of mucins in MEM and even less in correlating laboratory findings to bedside observations in patients suffering from OM. Answering the questions posed by our Central Hypothesis that specific host and pathogen factors influence mucosal changes to regulate GFM in the middle ear will allow significant enhancement in our understanding ME mucin function and regulation in relation to OM pathogenesis. The current proposal will include clinical specimens from children with chronic OM, animal models and in vitro cell culture models and employ molecular techniques to answer these fundamental questions: 1) What is the relationship of specific GFM to hearing loss in children, 2) Are there measurable changes in the MEM of children with chronic OM that correlate with changes in GFM?, 3) Does utilization of antibiotic therapy have a meaningful effect on GFM?, 4) What is the impact of biofilm formation on GFM in the ME space?, 5) In patients with chronic OM, do any of the primary OM pathogens: NTHi, SP or Mcat differentially regulate increased GFM production, 6) Does aquaporin 5 impact GFM regulation and 7) Is there a correlation between GFM expression and polymicrobial infection of OM pathogens? Data generated through this proposal will provide answers to these questions and will continue to advance our long-term goal of developing novel interventions in OM pathogenesis through modulation of mucin production pathways. PUBLIC HEALTH RELEVANCE: Ear infections affect almost all children, are an expensive burden on our health care system and are the most common cause of hearing loss in children; leading to potential developmental difficulties. Mucins are the fluids that build up behind the eardrums in some children after ear infections and cause the hearing loss. Understanding how these mucins form in children with chronic ear infections and developing new ways to treat and care for these children has the potential to lead to fewer children with hearing loss and other difficulties associated with this disease.